The equation of a circle $C$ is $x^2+y^2+2x-4y-44 = 0$. What is its center $(h, k)$ and its radius $r$ ?
Answer: To find the equation in standard form, complete the square. $(x^2+2x) + (y^2-4y) = 44$ $(x^2+2x+1) + (y^2-4y+4) = 44 + 1 + 4$ $(x+1)^{2} + (y-2)^{2} = 49 = 7^2$ Thus, $(h, k) = (-1, 2)$ and $r = 7$.